So far reporting in America has characterised the scandal as something that is limited to the UK, but senior executives are increasingly worried that it will cause lasting damage to the whole company.

Separately, Simon Witts, who as head of its Worldwide Enterprise and Partner group ran a third of Microsoft's business worldwide, has left the computer giant "by mutual consent" after 18 years of service.

There is no suggestion that he has been involved in the scandal, although he is named in High Court documents as being a key advocate of Simon Negus, the executive who is suing Microsoft for £10m for harassment and wrongful dismissal.

Mr Negus was alleged to have kissed a colleague, Toni Knowlson, at a wild company party in Atlanta, as well as to have engaged in "flirting and touching" with Ms Knowlson at a third colleague's leaving dinner in what was described as a pattern of sexual harassment.

He was also accused of asking a senior executive, Martina Milligan, to stand on a chair so people could see her short skirt, and of asking another Microsoft worker, Zobia Changthai, to "flutter her eyelashes".

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The claims were unproven but Mr Negus was ultimately dismissed for a "breach of trust" during an investigation into the allegations, and Microsoft launched legal action against him to recover £75,000 of a £225,000 "golden handshake".

However, Mr Negus, who was second in command at Microsoft UK and ranked as the corporation's top "level 69" partner worldwide, is counter-suing Microsoft for harassment and wrongful dismissal.

The investigation has laid bare apparently widespread drunkenness and harassment by Microsoft executives.

These culminated at the Microsoft Global Exchange party in Altanta, where sexual advances and a near punch-up – not involving Mr Negus – forced one executive, Emma Cloney, to flee under "protection", according to witness statements.

Mr Negus, claims that Gordon Frazer, managing director of Microsoft UK, whom he was hired to eventually succeed, deliberately obstructed his advancement.

It is alleged that Mr Frazer routinely excluded Mr Negus from management meetings, telling him Mr Negus and his team were not "true Microsoft people" and that if Microsoft UK's leadership team were "a reality TV show, and the team had to vote 'who got thrown off the island first'", Mr Negus would be the one to go, according to the documents.

Mr Negus reported directly to Mr Frazer, but had a "dotted" reporting line to Mr Witts, who had been instrumental in Mr Negus' appointment and continued to endorse him throughout his time at the company.

According to court filings, when Mr Negus complained to Mr Frazer about being excluded from meetings, the latter "responded aggressively, saying, 'Tell your friend Simon that I run the UK, not him.'"

According to sources close to the company, Mr Witts was regarded as having had an "excellent year" in terms of performance, but left suddenly following a meeting with Microsoft's chief operating officer, Kevin Turner.

Mr Turner issued a statement on Tuesday: "By mutual agreement, Simon Witts has decided to resign from Microsoft," it said.

Mr Witts did not return calls and Microsoft declined to comment further on his departure or whether he has a job to go to, although sources close to the company pointed out that a number of senior managers have left in recent years.

Microsoft's shares vested on August 30, meaning that he would have been in line for a significant payout.

Microsoft added in a statement: "These claims have been made by a former employee who was dismissed for gross misconduct nearly a year ago as a result of lying to senior management.

"It would be inappropriate to comment on the details of an ongoing legal case, other than to say we will be vigorously defending it."